1. Field of the Invention
Apparatuses consistent with the present invention relate to a perpendicular magnetic recording head and, more particularly, to a perpendicular magnetic recording head, which improves the shape of a sub-yoke so as to apply a sufficient magnetic field to record data on a recording medium, even with a main pole having a small pole tip.
2. Description of the Related Art
A magnetic recording method may be mainly classified into a longitudinal magnetic recording method and a perpendicular magnetic recording method. The longitudinal magnetic recording method, involves magnetizing a magnetic layer in a direction parallel to the surface of the magnetic layer to record data, and the perpendicular magnetic recording method involves recording data magnetizing the magnetic layer in a direction perpendicular to the surface of the magnetic layer to record data. Since the perpendicular magnetic recording method is much superior in terms of recording density as compared to the longitudinal magnetic recording method, perpendicular magnetic recording heads having various structures are being developed.
Referring to FIG. 1, a related art perpendicular magnetic recording (PMR) head includes a perpendicular magnetic recording medium 10 (hereinafter, a recording medium 10), a recording head 20 for recording data on the recording medium 10, and a read head 30 for reading data recorded on the recording medium 10.
The recording head 20 includes a main pole 22, a return yoke 24, and a coil 26. The coil 26 functions to generate a recording magnetic field required for recording data on the recording medium 10. The main pole 22 and the return yoke 24 form a magnetic path of the recording magnetic field generated by the coil 26, and are formed of a magnetic material, such as NiFe. By controlling the Ni and Fe content, the main pole 22 and the return yoke 24 may have appropriate saturation flux density Bs and magnetic permeability. A sub-yoke 28 is disposed on one side of the main pole 22 and forms the magnetic path of the recording magnetic field along with the main pole 22 and the return yoke 24.
The read head 30 includes first and second shields 32 and 34 and a read sensor 36 interposed between the first and second shields 32 and 34.
The recording medium 10 includes a soft-magnetic underlayer 11, an intermediate layer 12, and a recording layer 13. When current is supplied to the coil 26, a magnetic field that is generated around the coil 26 forms a magnetic path that leads from an end tip of the main pole 22 through the soft-magnetic underlayer 11 to the return yoke 24. In this case, a magnetic domain of the recording layer 13 is magnetized by a perpendicular component of the magnetic field so that data is recorded on the recording layer 13.
A magnetized unit is referred to as a recording bit, and the recording density is conventionally referred to as an areal density, which is calculated as the number of recording bits per 1 inch2. In order to increase the areal density, the lengths of the recording bit measured in both a down track direction and a cross track direction should be reduced. The length of the recording bit measured in the down track direction depends on the moving speed of the recording medium 10, the frequency of a recording current, and the length of an end tip of the main pole 22 near the recording medium 10 (i.e., the length of a pole tip of the main pole 22) measured in the down track direction. Also, the length of the recording bit measured in the cross track direction depends on the length of the pole tip measured in the cross track direction. That is, the size of the pole tip should be reduced to increase the areal density. However, as the size of the pole tip decreases, a magnetic field generated from the pole tip decreases and recording characteristics deteriorate, thus making it difficult to increase the recording density. Therefore, a problem resulting in the reduction in a magnetic field should be solved in order to increase the recording density and achieve a stable recording characteristic.